The relative abundance of methane in natural gas and high cost of petroleum raw materials has led workers in the field of fossil fuel technology to seek economic processes for conversion of lower alkanes to higher hydrocarbons in the gasoline and diesel range for use as liquid fuels. The C.sub.5.sup.30 aliphatic and aromatic hydrocarbons are particularly useful as spark-ignited fuel for internal combustion engines. Steam reforming of methane-rich feedstocks to produce CO and H.sub.2 syngas can be followed by conventional methanol synthesis or Fischer-Tropsch reactions to provide oxygenated feedstock suitable for hydrocarbon conversion over a particular class of crystalline medium pore zeolites, known as ZSM-5 catalysts.
A substantial effort has been made in developing a methanol-to-gasoline ("MTG") process, as described in U.S. Pat. Nos. 3,894,107 (Butter et al), 4,013,731 (Chang et al), 4,118,431 (Chen), 4,251,484 (Daviduk et al). Other disclosures involving ZSM-5 type catalysts for converting synthesis gas to gasoline-range hydrocarbons are U.S. Pat. 4,159,995 (Haag et al), 4,093,029 (Weisz et al).